# Insight into the Microbiota of Orthopteran in Relation to Gut Compartmentalisation

## TL;DR

This paper reviews the gut microbiota of orthopteran insects, highlighting their functional diversity and how gut compartmentalization affects microbial communities.

## Contribution

The paper provides a synthesis of scattered data on orthopteran gut microbiota and identifies potential roles in digestion and pheromone production.

## Key findings

- Some gut bacteria like Pantoea and Enterobacter may be involved in cellulose degradation.
- Midgut bacteria are linked to amino acid synthesis, while hindgut bacteria may be involved in catabolism.
- P. agglomerans might contribute to pheromone production in desert locusts.

## Abstract

Orthoptera are a very diverse and globally distributed order of insects. They provide important services in grassland ecosystems, such as organic matter decomposition and vegetation renewal. They also include species that are important crop pests and are increasingly used in the insect farming industry for food and feed. Despite their ecological and economic importance, the functional diversity of their gut-associated microbiota has received little attention compared to other insect groups. However, unravelling the microbiological dimension of these insects is crucial to better understand the role of microorganisms in the evolutionary success of these mainly herbivorous insects and to optimize their rearing conditions with a view to industrial bioconversion processes and as alternative food resources.

This review first provides an overview of the functional diversity of Orthoptera-associated microbiota and the services they provide to their hosts. However, data are widely scattered across the different families studied, making it difficult to establish whether a core microbiota is present. The abundance of some genera (Pantoea, Enterococcus, Enterobacter, Acinetobacter) is associated with the degradation of cellulose compounds, although their clear contribution remains to be determined. In addition, P. agglomerans may play a role in the production of aggregation pheromones in the desert locust. In terms of gut compartmentalisation, the diversity of the bacterial community in the foregut appears to be highly variable between individuals and species, whereas it is more uniform in other parts of the gut. Metabolic pathways of the gut microbiota revealed differences in amino acid metabolism between the midgut and hindgut. Bacteria in the midgut are associated with amino acid synthesis and anaerobic metabolism, whereas pathways in the hindgut may be involved in amino acid catabolism and ace-tyl-CoA-mediated processes. Further research is needed to better understand these different components of the bacterial community in digestive processes, and to identify bacterial species of particular interest in explaining species’ lifestyles or for bioconversion.